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Communications Protocol

•All communications between devices require that thedevices agree on the format of the data. The set of rulesdefining a format is called aprotocol. At the very least,a communications protocol must define the following:

•rate of transmission (in baud or bps)

•whether transmission is to besynchronous orasynchronous

•whether data is to be transmitted inhalf-duplex or full-duplex mode

•In addition, protocols can include sophisticatedtechniques for detecting and recovering fromtransmission errors and for encoding and decoding data.

TCP/IP Model

1-25-06

Layer

Name

Common

Components

OSI

Reference

Application

HTTP, SMTP, POP3

FTP, DNS

Application

Presentation

Session

Transport

TCP, UDP

Transport

Network

IP, ICMP

Network

Physical

Ethernet, FDDI

Data Link

Physical

TCP/IP Protocols

•Hypertext Transfer Protocol (HTTP)

–Web servers implement this protocol. Shortfor HyperText Transfer Protocol, theunderlying protocol used by the World WideWeb. HTTP defines how messages areformatted and transmitted, and what actionsWeb servers and browsers should take inresponse to various commands. For example,when you enter a URL in your browser, thisactually sends an HTTP command to the Webserver directing it to fetch and transmit therequested Web page.

TCP/IP Protocols

•Simple Mail Transfer Protocol (SMTP)

–Used by e-mail servers (and sometimes Web servers)to send e-mail. Short for Simple Mail TransferProtocol, a protocol for sending e-mail messagesbetween servers. Most e-mail systems that send mailover the Internet use SMTP to send messages fromone server to another; the messages can then beretrieved with an e-mail client using either POP orIMAP. In addition, SMTP is generally used to sendmessages from a mail client to a mail server. This iswhy you need to specify both the POP or IMAP serverand the SMTP server when you configure your e-mailapplication.

TCP/IP Protocols

•Post Office Protocol Version 3 (POP3)

–A protocol used to retrieve e-mail from a mail server.Most e-mail applications (sometimes called an e-mailclient) use the POP protocol, although some can usethe newer IMAP (Internet Message Access Protocol).

–There are two versions of POP. The first, calledPOP2, became a standard in the mid-80's andrequires SMTP to send messages. The newerversion, POP3, can be used with or without SMTP.

TCP/IP Protocols

•IMAP

-

Short for Internet Message AccessProtocol, a protocol for retrieving e-mailmessages. The latest version, IMAP4, is similarto POP3 but supports some additional features.For example, with IMAP4, you can searchthrough your e-mail messages for keywordswhile the messages are still on mail server. Youcan then choose which messages to downloadto your machine.

•IMAP was developed at Stanford University in1986.

TCP/IP Protocols

•File Transfer Protocol (FTP)

–The protocol for exchanging files over the Internet.FTP works in the same way as HTTP for transferringWeb pages from a server to a user's browser andSMTP for transferring electronic mail across theInternet in that, like these technologies, FTP uses theInternet's TCP/IP protocols to enable data transfer.

–FTP is most commonly used to download a file from aserver using the Internet or to upload a file to a server(e.g., uploading a Web page file to a server).

•DNS

–Short for Domain Name System (or Service orServer), an Internet service that translates domainnames into IP addresses. Because domain namesare alphabetic, they're easier to remember. TheInternet however, is really based on IP addresses.Every time you use a domain name, therefore, a DNSservice must translate the name into thecorresponding IP address. For example, the domainname www.example.com might translate to198.105.232.4.

–The DNS system is, in fact, its own network. If oneDNS server doesn't know how to translate a particulardomain name, it asks another one, and so on, untilthe correct IP address is returned.

TCP/IP Protocols

TCP/IP Protocols

Transmission Control Protocol (TCP)

–Creates a reliable connection between twocomputers. TCP is one of the main protocolsin TCP/IP networks. Whereas the IP protocoldeals only with packets, TCP enables twohosts to establish a connection and exchangestreams of data. TCP guarantees delivery ofdata and also guarantees that packets will bedelivered in the same order in which theywere sent.

•Internet Protocol (IP)

–Provides addressing scheme.. IP specifies the format of packets,also called datagrams, and the addressing scheme. Mostnetworks combine IP with a higher-level protocol calledTransmission Control Protocol (TCP), which establishes a virtualconnection between a destination and a source.

–IP by itself is something like the postal system. It allows you toaddress a package and drop it in the system, but there's nodirect link between you and the recipient. TCP/IP, on the otherhand, establishes a connection between two hosts so that theycan send messages back and forth for a period of time.

–The current version of IP is IPv4. A new version, called IPv6 orIPng, is under development.

Short for Request for Comments, a series ofnotes about the Internet, started in 1969.An InternetDocument can be submitted to the IETF by anyone,but the IETF decides if the document becomes anRFC. Eventually, if it gains enough interest, it mayevolve into an Internet standard.

TCP/IP Protocols

TCP/IP Protocols

•User Datagram Protocol (UDP)

–Does not establish a connection, just sendsmessages.

–a connectionless protocol that, like TCP, runs ontop of IP networks. Unlike TCP/IP, UDP/IPprovides very few error recovery services,offering instead a direct way to send and receivedatagrams over an IP network. It's used primarilyfor broadcasting messages over a network.

Connecting Your LAN to theInternet

•Your ISP connects to the Internet

•A WAN connection is used between yourbuilding and the ISP

•A T-Carrier connection is often used

–A digital connection for voice and data

Common T-Carrier Connections

Other ways to Connect to theInternet

•Integrated services digital network (ISDN)

–Dial-up access

–Basic Rate Interface (BRI) up to 128 Kbps

–Primary Rate Interface (PRI) up to 1.544 Mbps

•Digital Subscriber Line (DSL)

–Often differing speeds for uploads and downloads

–Depending on type, up to 6.1 Mbps for downloadsand 1.544 Mbps for uploads

•Cable Modem

–Shared access cable provided by cable TV company

With the addition of users in the area transfer speedswill be reduced.

Web Hosting Solutions

•Standard hosting

–Your site resides on the same computer with manyother sites

–Cheapest solution

•Dedicated server

–You have a server that only you use

•Co-location

–Your own server is physically located at the companythat does your Web hosting

Web Browsers

Browser Wars

•

A software application used to locate anddisplay Web pages. The two most popularbrowsers are Netscape Navigator andMicrosoft Internet Explorer. Both of theseare graphical browsers, which means thatthey can display graphics as well as text.In addition, most modern browsers canpresent multimedia information, includingsound and video, though they requireplug-ins for some formats.

Web Browsers

Netscape

•The creation

•Netscape Navigator was developed by the teamwho had created the Mosaic web browser at theNational Center for SupercomputingApplications. The company they created wasinitially named "Mosaic CommunicationsCorporation" and their web browser "Mosaic",but a legal challenge from NCSA over the rightsto the name resulted in the company and theproduct being renamed. The name "Netscape"was invented by sales representative GregSands.

Web Browsers

Mosaic Netscape 0.9

Web Browsers

Netscape

•Release history

•Mosaic Netscape 0.9–

October 13, 1994

•Netscape Navigator 1.0–

December 15, 1994

•Netscape Navigator 1.1

•Netscape Navigator 1.22

•Netscape Navigator 2.0–

September 18, 1995

•Netscape Navigator 2.01

•Netscape Navigator 2.02

•Netscape Navigator 3.0–

August 19, 1996

•Netscape Navigator 3.01

•Netscape Navigator 3.02

•Netscape Navigator 3.03

•Netscape Navigator 3.04–

October 4, 1997

•Netscape Navigator 4.0–

June 1997

Web Browsers

Netscape

The rise of Netscape

•When the consumer internet revolution arrived inthe mid to late 1990s, Netscape was wellpositioned to take advantage of it. With a goodmix of features and an attractive licensingscheme that allowed free use for non-commercial purposes, the Netscape browsersoon became the de facto standard, particularlyon the Windows platform.

Web Browsers

Netscape

The fall of Netscape

•Microsoft saw Netscape's success as a clearthreat to the dominant status of the MicrosoftWindows operating system. It began a wide-reaching campaign to establish control over thebrowser market. Browser market share, it wasreasoned, leads to control over internetstandards, and that in turn would provide theopportunity to sell software and services.Microsoft licensed the Mosaic source code fromSpyglass, Inc., an offshoot of the University ofIllinois, and turned it into Internet Explorer.

Web Browsers

Netscape

•The resulting battle between the two companiesbecame known as the browser wars. Versions ofIE were markedly inferior to contemporaryversions of Netscape Navigator; IE 3.0 (1996)began to catch up to its competition; IE 4.0(1997) was the first version that looked to haveNetscape beaten, and IE 5.0 (1998) with manybug fixes and stability improvements sawNavigator's marketshare plummet below IE forthe first time.

Web Browsers

Netscape

•In March 1998, Netscape released most of the code base forCommunicator under an open source license. The product namedNetscape 5, which was intended to be the result, was neverreleased, as managers decided that the code needed a completerewrite. This product, taking growing contributions from the open-source community, was dubbed Mozilla, once the codename of theoriginal Netscape Navigator. Netscape programmers gave Mozilla adifferent GUI and released it as Netscape 6 and later Netscape 7.After a lengthy public beta, Mozilla 1.0 was released on June 5,2002. The same code base, most notably the Gecko layout engine,became the basis of several standalone applications, includingFirefox and Thunderbird.

•These products, however, came too late for Netscape as abusiness. Eventually Microsoft emerged victorious in the browserwars, and Netscape was acquired in 1999 by AOL.

Web Browsers

Internet Explorer

•Internet Explorer 3 was the first majorbrowser withCascading Style Sheets

(CSS) support released in August, 1996and it could handle the PICS system forcontent metadata. The improvementswere significant, compared to its maincompetitor at the time, NetscapeNavigator.

Web Browsers

Internet Explorer

•The browser was not widely used untilversion 4, which was released in October1997 and was integrated with theWindows 98 operating system. Thisintegration, however, was subject tonumerous criticisms (see United States v.Microsoft). Version 5, released inSeptember 1998, was another significantrelease that supported bi-directional text,ruby characters, XML and XSL.

Web Browsers

Internet Explorer

•Version 6 was released on August 27, 2001, afew weeks before Windows XP. This versionincluded DHTML enhancements, contentrestricted inline frames, and better support ofCSS level 1, DOM level 1 and SMIL 2.0. TheMSXML engine was also updated to version 3.0.Other new features included a new version ofthe IEAK, Media bar, Windows Messengerintegration, fault collection, automatic imageresizing, P3P, and a new look-and-feel that is inline with the style of Windows XP

•For version 7.0 of Internet Explorer, set to ship withWindows Vista and as a separate download for WindowsXP with Service Pack 2, large amounts of thearchitecture, including the security framework, havebeen completely overhauled. Partly as a result of thesesecurity enhancements, the browser will be a stand-alone application, rather than integrated with theWindows shell, and it will no longer be capable of actingas a file browser. The "beta 1" (build 5112) and "beta 2preview" (build 5299) pre-releases both operate in thisnew stand-alone manner.

Web Browsers

Internet Explorer

Web Browsers

Developing Web sites For

•Browsers have been criticized for implementing non-standard HTMLmarkup extensions such as the BLINK tag, which is sometimesreferred to as a symbol for Netscape's urge to develop extensionsnot standardized by the W3C, and even mentioned in the fictionalBook of Mozilla. Both IE and Netscape have also been criticized forfollowing actual web standards poorly, often lagging behind orsupporting them very poorly or even incorrectly. This criticism wasn'tvery loud during the days of its popularity as web masters then oftensimply developed for Netscape Navigator, but came to be anincreasing annoyance to webmasters who wish to provide backwardand cross-browser compatibility. Today, many web masters stillstruggle with cross-browser compatibility do not choose to supportold versions, due to their poor and invalid web standardimplementations.

100

100

200

400

400

Browsers

Netscape

Internet Explorer

300

300

300

200

400

200

500

500

500

100

Row 1, Col 1

Flash, Acrobat Reader

What are Browser Plug-ins?

1,2

Greg Sands

Who came up with the Name Netscape?

1,3

IE

What is Internet Explorer?

1,4

P-Card

What is a payment method available for purchases up to$4999.99 for which a blanket contract does not exist?

2,1

A software application used to locate and

display Web pages

What is a Web browser?

2,2

TRUE OR FALSE

The Netscape Browser came after

Microsoft’s Internet Explorer

What is False?

2,3

CSS

What areCascading Style Sheets

?

2,4

Receipt and invoice

Which payment method can be used for all purchases?

3,1

NCSA

What is the National Center for

Supercomputing Applications?

3,2

AOL

Who Acquired Netscape in 1999?

3,3

Spyglass, Inc

Who did Microsoft License it’s IE Source Code From?

3,4

Petty Cash

What is a payment method that can be used forpurchases up to $100?

4,1

Netscape Navigator and

Microsoft Internet Explorer

What are the two most popular browsers

?

4,2

Mosaic

What was Netscape Initially Called?

4,3

Version 7.0

What is IE’s Latest Version?

4,4

Direct Demand

What is a payment method that can be used forpurchases up to $5,000.00?